1. Field of the Invention
The present invention relates to a method of connecting covered wires, by which respective conductors of the covered wires can be connected to each other by making use of internal heating of the wires brought by ultrasonic oscillation. More particularly, it relates to a connecting method for covered wires, which is effective to connect a shield wire with a ground wire.
2. Description of the Related Art
Generally, it is complicated and troublesome to handle a shield wire having a braided wire coaxially disposed around a core line (or core lines) with the deteriorated workability in using the shield wire. As an effective measure for improving the deteriorated workability, there is provided a connecting structure for wires which takes advantage of inside heating due to the ultrasonic oscillation by Japanese Unexamined Patent Publication (kokai) No. 7-320842.
In the publication, there are shown two kinds of covered wires. One is a shield wire which comprises a core line, an inside insulating rind arranged outside the core line, a braided wire as a shield conductor arranged outside the inside insulating rind, and an outside insulating rind. The other is a ground wire consisting of a core line and an outside resinous rind arranged outside the core line.
According to the disclosed method, in order to connect the braided wire of the shield wire with the core line of the ground wire in front of the connector, the shield wire and the ground wire being both connected to a connector, the ground wire is firstly overlaid on the shield wire so as to cross each other at a connection point. Next, the overlapping portions are interposed between upper and lower resin tips. Then, while compressing the upper and lower resin tips from the outside, they are subjected to ultrasonic oscillation by making use of an ultrasonic horn and an anvil. Consequently, both of the outside rinds of the shield wire and the ground wire are molten for elimination, so that the braided wire of the shield wire comes into electrical contact with the core line of the ground wire. Simultaneously, the upper and lower resin tips are mutually welded to each other thereby to seal up the surroundings of the above connecting point.
There is proposed a modified method of connecting the core line of the ground wire with the braided wire of the shield wire by brazing. In this modified method, a metal piece (brazing metal) capable of melting at relatively low temperature is embedded in the upper resin tip in advance of welding. And then, on condition that the shield wire and the ground wire are interposed between the upper resin tip and the lower resin tip, they are subjected to the ultrasonic oscillation. Consequently, the core line of the ground wire can be brazed to the braided wire of the shield wire through the intermediary of the metal piece molten by the ultrasonic oscillation.
It should be noted in the above method that the upper and lower resin tips used are respectively provided, on mutual butt surfaces thereof, with shallow grooves for accommodating the shield wire therein. The above metal piece is embedded in a recess in the shallow groove formed in the upper resin tip and positioned so that a top of the piece somewhat projects from a bottom of the shallow groove.
In the above-mentioned method, however, the molten metal cannot dissolve into a contact between the braided wire and the core line unless the insulating covers of the shield wire and the ground wire are not molten and removed sufficiently. That is, despite that the ultrasonic oscillation is applied on the lower resin tip and the upper resin tip having the metal piece embedded therein, there is still remained a difficulty of brazing the braided wire to the core line certainly. For this reason, the resultant structure connected in accordance with this method does exhibit wide dispersion in terms of its electrical performance after thermal shock test.
Under such a circumstance, it is therefore an object of the present invention to provide a connecting method for covered wires, which allows the above metal piece soluble at relatively low temperature, to dissolve into the circumference of a contact between conductors of the covered wires certainly.
The object of the present invention described above can be accomplished by a method for connecting conductors of covered wires to each other, the method comprising:
a first process including the steps of:
preparing a first covered wire having a first conductor covered with an insulating cover and a second covered wire having a second conductor covered with another insulating cover;
overlaying the second covered wire on the first covered wire so as to cross each other;
putting overlapping portions of the first and second wires between an upper resin tip and a lower resin tip; and
melting and removing the insulating covers of the first and second wires in the vicinity of the overlapping portions by a first ultrasonic oscillation; and
a second process including the steps of:
setting a brazing metal on a contact between the first conductor and the second conductor, the contact being exposed by removing the insulating covers of the first and second wires; and
melting the brazing metal to braze the contact by a second ultrasonic oscillation.
According to the above-mentioned method, since the first and second conductors are brazed to each other after removing the insulating covers of the first and second wires, it is possible to melt the brazing metal into the contact of the first and second wire, sufficiently.
In the above-mentioned method, preferably, the upper resin tip is provided, at a center thereof, with a through hole and the first ultrasonic oscillation at the first process is carried out by inserting a projection of an ultrasonic horn into the through hole of the upper resin tip, thereby oscillating the overlapping portion with ultrasonic waves, directly; and the second ultrasonic oscillation at the second process is carried out by previously inserting the brazing metal into the through hole and sequentially inserting a resin piece into the through hole.
According to the preferred method, since the projection of the ultrasonic horn inserted into the through hole applies the ultrasonic oscillation on the first and second covered wires directly, it is possible to eliminate the insulating covers of the wires effectively, whereby the contact of the first and second conductors can be exposed. Furthermore, at the second step, by inserting the brazing metal and the resin piece into the through hole, the brazing metal can dissolve in the exposed contact only, so that the certain metal binding can be accomplished.
In the above-mentioned method, preferably, the first covered wire is a shield wire having a shield conductor as the first conductor, while the second covered wire is a ground wire having a core line as the second conductor.
In this case, owing to the first and second ultrasonic oscillations, it is possible to connect the shield conductor of the shield wire to the core line of the ground wire certainly.
According to the present invention, there is also provided a method for connecting conductors of covered wires to each other, the method comprising:
a first process including the steps of:
preparing a first covered wire having a first conductor covered with an insulating cover and a second covered wire having a second conductor covered with another insulating cover;
overlaying the second covered wire on the first covered wire so as to cross each other;
putting overlapping portions of the first and second wires between an upper resin tip and a lower resin tip; and
melting and removing the insulating covers of the first and second wires in the vicinity of the overlapping portions by a first ultrasonic oscillation; and
a second process including the steps of:
setting a brazing metal on a contact between the first conductor and the second conductor, the contact being exposed by removing the insulating covers of the first and second wires; and
applying a second ultrasonic oscillation on the upper and lower resin tips while pressurizing them from the outside, thereby melting the brazing metal to braze the contact and also mutually welding the upper and lower resin tips to each other to seal up the circumference of the contact by the welded resin tips.
Also in the above method, after removing the insulating covers of the first and second wires, the first and second conductors are brazed to each other through the brazing metal. Thus, it is possible to melt the brazing metal into the contact of the first and second wire, sufficiently.
According to the present invention, there is also provided a method for connecting conductors of covered wires to each other, the method comprising:
a first process including the steps of:
preparing a first covered wire having a first conductor covered with an insulating cover and a second covered wire having a second conductor covered with another insulating cover;
overlaying the second covered wire on the first covered wire so as to cross each other;
putting overlapping portions of the first and second wires between an upper resin tip and a lower resin tip; and
applying a first ultrasonic oscillation on the upper and lower resin tips, thereby melting and removing the insulating covers of the first and second wires in the vicinity of the overlapping portions and also mutually welding the upper and lower resin tips to each other to seal up the circumference of the overlapping portions by the welded resin tips; and
a second process including the steps of:
setting a brazing metal on a contact between the first conductor and the second conductor, the contact being exposed by removing the insulating covers of the first and second wires; and
melting the brazing metal to braze the contact by a second ultrasonic oscillation.
Also in the above method, after removing the insulating covers of the first and second wires, the first and second conductors are brazed to each other through the brazing metal. Thus, it is possible to melt the brazing metal into the contact of the first and second wire, sufficiently.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompany drawings.